Concrete is a widely used construction material. In general, concrete comprises cement, coarse and fine aggregates, and chemical additives. Concrete is conventionally cured in the presence of water to optimize cement hydration. The water reacts with the cement, bonding the components together and forming a solid article of manufacture. Concrete strength and water-resistance improves when cement is thoroughly hydrated during curing. Proper curing slows the loss of moisture from concrete and reduces early carbonation of the surface. Excessive evaporation and drying of concrete inhibits hydration. If drying is excessive, light traffic on a concrete surface may result in dusting. Moreover, craze cracking often may be attributed to inadequate curing.
A concrete surface is conventionally kept wet during curing by applying water frequently thereto and then covering the surface with a moisture retaining material. Material, such as burlap, conventionally is placed on a newly poured concrete surface as soon as possible without marking the concrete surface. The material is kept continuously wet and in place as long as possible. To ensure continuity of moist curing under the material, and without intermittent drying, a plastic (e.g., polyethylene) sheet is conventionally laid on top of the material to serve as a moisture barrier.
Conventional covering materials, however, can cause non-uniform coloration (“blotchiness”) in cured concrete. Surface blotchiness may be accentuated by plastic barrier materials that are exposed to sunlight during curing. Furthermore, incomplete contact between the moisture retaining material and concrete surface as a result of trapped air pockets may lead to concrete discoloration.
A conventional concrete curing blanket 10 is illustrated in FIGS. 1A and 1B. The illustrated concrete curing blanket 10 includes a layer of absorbent material 12 and a layer of impervious material 14 laminated to the absorbent material layer 12 in face-to-face contact with each other, for example via an adhesive layer 17, to form a composite article. In use, the concrete curing blanket 10 is placed on a surface 16a of a poured concrete slab 16 such that the absorbent material layer 12 is in contact with the surface 16a, as illustrated in FIG. 1A. Air trapped beneath the concrete curing blanket 10 may create air bubbles 20 that cause the concrete curing blanket 10 to lift away from the concrete surface 16, as illustrated in FIG. 1B, thereby causing surface blotchiness.